1. Field of the Invention
The present invention relates to non-magnetic ceramics for recording/reproducing heads used for a ceramic substrate for thin-film magnetic heads, for a slider for a variety of magnetic heads, for a spacer for magnetic heads, for a guide for magnetic recording tapes, etc., and to a method of producing the same. In particular, the invention relates to non-magnetic ceramics for recording/reproducing heads that makes it possible to prepare a head that is highly precisely machined owing to its large hardness and large Young's modulus and to provide a data recording device featuring excellent reliability, the non-magnetic ceramics for recording/reproducing heads exhibiting a small frictional force and adhesive force with respect to the recording disks and the recording tapes which are recording media having a high density.
2. Description of the Prior Art
In recent years, the effort for increasing the density of magnetic recording has been realized at an ever rapid rate. Accompanying this tendency toward ever higher recording density, attention has now been given to a thin-film head which utilizes a thin magnetic film and is adapted to increasing the density of magnetic recording, and which can be used as a recording/reproducing magnetic head for media of high coercive force such as hard disk, 8-mm VTR, electronic still camera, video floppy, digital audio equipment, etc. to substitute for the conventional magnetic heads using ferrite or the like.
A thin-film head utilizing a thin magnetic film is obtained, for example, as described below. First, on the surface of a substrate which is 6 inches or 3 inches in diameter is formed an insulating film of alumina by sputtering, and several thousands of transducers are formed on the upper surface of the alumina film relying upon lithography. An alumina insulating film is formed again on the substrate on which the transducers have been formed. The individual magnetic heads are then cut out from the substrate by taking into consideration the polishing margin which serves as a slider. The bar members that are cut out and are including the thin-film heads, are then polished on their surfaces on one side to obtain slide surfaces.
Accompanying an increase in the recording density of the Winchestor-type magnetic head in recent years, however, the flying height of the magnetic head over the surface of the disk is decreasing down to the order or submicrons or smaller. Due to a difference in the peripheral speed between the inner periphery and the outer periphery of the magnetic disk, however, the flying height of the slider undergoes a change. In order to decrease the change in the floating amount, it has heretofore been proposed not only to provide a positive pressure portion on the air bearing surface as in a customary manner but also to form a negative pressure portion by forming tiny grooves (recessed portions) in part of the slide surface, in an attempt to uniformalize the floating amount of the head from the inner periphery through up to the outer periphery of the disk.
Because of the above-mentioned reasons, therefore, the slide surface which is one of the surfaces of the bar member cut out from the substrate is polished and, then, grooves (recessed portions) are formed in the slide surface. The grooves are usually formed by machining. When a negative-pressure slider is to be formed, the grooves will be formed in a size of several microns by milling using an ion beam, milling using reactive ions, chemical etching, etc.
In the conventional thin-film head, the bar member for slider is warped by several microns per a length of 50 mm at the time of cutting out the bar member and the depth of magnetic gap (throat height) in the slide surface changes by several microns without, however, affecting the electric properties in relation to the reproduction and recording.
In the magnetic head for high-density recording, however, variation in the gap depth caused by warping deteriorates the electric properties. Therefore, the amount of warping must be in the order of submicrons or smaller per a length of 50 mm in a state where the bar member for slider is cut out. In the magnetic heads for high-density recording, an alumina/titanium carbide material has heretofore been used as a slider material. With the material of this type, the warping can be decreased to some extent in a state where the bar member slider is cut out, which warping, however, is still so great that a large load is produced during the cutting operation by using a diamond grinder, and the cutting is not accomplished within short periods of time maintaining precision.
In forming grooves in the bar for slider, furthermore, the slide surface must be finely machined by ion milling, etc. In this case, the machining time and the uniformity in the machined surface are important factors in the production from the standpoint of mass productivity and precision. Using the conventional alumina/titanium carbide composite material, however, the milling rate is small and the surface becomes rugged to a large extent after the milling. In recent years, therefore, it has been demanded to provide a material which can be milled at an increased rate and acquires small ruggedness in the surface after milling.
Moreover, the conventional slider material composed of alumina/titanium carbide for thin-film heads exhibits a large adhesive force or a frictional force with relative to the disk, which could result in a trouble such as head crash impairing the reliability of the data recording device to a serious degree. Even from the standpoint of improving reliability of the magnetic head, it has been urged to provide a material having excellent slide properties, suppressing the frictional force and the absorptive force between the magnetic head and the disk.
In order to reduce the frictional force or the adhesive force between the recording disk and the recording/reproducing head, there has been proposed to form a crown or the like on the air bearing surface of the head. In this case, however, the size of the crown is of the order of several nanometers which can be realized by using a machining jig and a device of very high precision making it, therefore, difficult to mass-produce the heads at a reduced cost.